I take your point about water, I will have a tap installed (mainly to
fill my kettle) I would like to use a water butt but haven't the
experience for the advantages of keeping it inside to be obvious, I can
only think of not having to carry the water as far. Does the water in a
butt get smelly and stagnant? and wouldn't it take up valuable space
inside the greenshouse? sorry if I am being unbearably stupid.


Quick answer from a non gardener. If you have your water butt inside the
greenhouse, it will always be at greenhouse temperature :-)) AND, if you
keep a lid on it, A) The wildy beasties won't get in and B) it should not go
green and nasty :-))

Mike
A non gardener but learning fast from 'her out of doors' and the
patio/path/bed/fence making I am asked to do :-((
(Now a plumber/tiler/shower installer/under floor tile heating
expert/carpenter etc etc)